in a flame of fire: Heb. בִּלַבַּת אֵשׁ, in a flame of (שַׁלְהֶבֶת) fire, the heart (לִבּוֹ) of fire, like “the heart (לֵב) of the heavens” (Deut. 4:11), “in the heart (בְּלֵב) of the terebinth” (II Sam. 18:14). Do not wonder about the tav [in לִבַּת], for we have [an instance] similar to this: How degenerate is your heart (לִבָּתֵ) (Ezek. 16:30).

for I know their pains: This is similar to: “and God knew” (Exod. 2:25). That is to say: for I set My heart to contemplate and to know their pains, and I have not hidden My eyes, neither will I block My ears from their cry.

8I have descended to rescue them from the hand[s] of the Egyptians and to bring them up from that land, to a good and spacious land, to a land flowing with milk and honey, to the place of the Canaanites, the Hittites, the Amorites, the Perizzites, the Hivvites, and the Jebusites.

And He said, “For I will be with you…”: He [God] answered his former [question] first, and his latter [question] last. [Concerning] what you said, “Who am I that I should go to Pharaoh?” This [mission] is not yours but Mine, “for I will be with you.” And this vision which you have seen in the thorn bush, is the sign for you that it was I who sent you and that you will succeed in My mission and that I am able to save you. Just as you saw the thorn bush performing My mission and not being harmed, so will you go on My mission and not be harmed. [Concerning] what you asked, “what merit do the Israelites have that they should go out of Egypt?” I have a great thing [dependent] on this Exodus, for at the end of three months from their Exodus from Egypt they are destined to receive the Torah on this mountain. Another explanation: For I will be with you, and this [namely] that you will succeed in your mission [on which I am sending you] is the sign for you for another promise, which I promise you, [namely,] that when you take them out of Egypt, you will serve God on this mountain, for you will receive the Torah on it, and that is the merit that will stand up for Israel. Similar to this expression [where a future event serves as a sign for a still more distant event], we find: “And this shall be the sign (הָאוֹת) for you, this year you shall eat what grows by itself, etc.” (Isa. 37:30, II Kings 19:29). Sennacherib’s downfall will be a sign for you regarding another promise, [i.e.,] that your land is desolate of fruit, and I will bless what grows by itself.

“Ehyeh asher ehyeh (I will be what I will be)”: “I will be” with them in this predicament “what I will be” with them in their subjugation by other kingdoms. He [Moses] said before Him, “O Lord of the universe! Why should I mention to them another trouble? They have enough [problems] with this one.” He said to him, “You have spoken well. So shall you say, etc.” -[from Ber. 9b] (Not that Moses, God forbid, outsmarted God, but he did not understand what God meant, because originally, when God said, “I will be what I will be,” He told this to Moses alone, and He did not mean that he should tell it to Israel. That is the meaning of “You have spoken well,” for that was My original intention, that you should not tell such things to the children of Israel, only “So shall you say to the children of Israel,” ‘Ehyeh [I will be] has sent me.’” From tractate Berachoth this appears to be the correct interpretation. Give this matter your deliberation.) [Annotation to Rashi] [There appears to be no indication of this interpretation in tractate Berachoth.]

15And God said further to Moses, "So shall you say to the children of Israel, 'The Lord God of your forefathers, the God of Abraham, the God of Isaac, and the God of Jacob, has sent me to you.' This is My name forever, and this is how I should be mentioned in every generation.

This is My name forever: Heb. לְעֹלָם [It is spelled] without a vav, meaning: conceal it [God’s name] תהַעִלִימֵהוּ [so] that it should not be read as it is written. — [from Pes. 50a] Since the “vav” of (לְעֹלָ ם) is missing, we are to understand it as לְעַלֵּם, to conceal, meaning that the pronunciation of the way God’s name is written (י-ה-ו-ה) is to be concealed. — [from Pes. 50a.]

זה שמי לעלם: חסר וי"ו, לומר העלימהו, שלא יקרא ככתבו:

and this is how I should be mentioned -: He [God] taught him [Moses] how it was to be read, and so does David say, “O Lord, Your name is forever; O Lord, the mention of Your name is for every generation” (Ps. 135:14). — [from Pes. 50a]